The present invention relates to a generating control device for a hybrid vehicle which includes an engine, a generator driven by the output of the engine, a battery and a control unit for controlling operations of these elements.
In recent years, a series hybrid electric vehicle (SHEV) equipped with a generator-and an engine for driving it, has been developed in order to increase a cruising range of an electric vehicle. In this art, it is also known a system which is installed in the hybrid vehicle and which allows it to travel by electric energy supplied from a battery when the battery is charged fully. On the other hand, when the charged energy in the battery decreases, the system starts the engine in order to charge the battery by electric power supplied from the generator. Thereafter, when the charging amount reaches a prescribed value, the engine is inacivated.
In such a series hybrid electric vehicle, if the engine of the vehicle is used little in comparison with that of a gasoline-fueled automobile (not electrical car), the vehicle exhibits a low-pollution car on one hand. On the other hand, depending on methods of controlling the engine and the generator, there is a possibility to cause pollution problems equal to or greater more than those of the gasoline-fueled automobile.
Furthermore, it is supposed that, depending on the control method of the generator, repeated overcharging or overdischarging operations for the battery may cause the battery's life span to be shortened in comparison with that of an electric car, so that cost and time for exchanging the battery (or batteries) with another may be increased disadvantageously.
In the prior art, for example, Japanese Unexamined Patent Publication (Kokai) No. 5-32852 discloses one of the conventional generating control devices for the hybrid vehicles. This generating control device operates to drive the generator for assisting the battery in response to loads of the drive motor in the hybrid electrical vehicle, while the device judges the loads according to the charged energy in the battery, an opening of an accelerator pedal, degree of slope etc. and adjusts an opening of a throttle valve.
In the above-mentioned conventional generating control device of the hybrid vehicle, however, the battery deteriarates quickly since the device is not able to determine if the battery cannot be charged or discharged.